I beg to differ. The A1 barrel was the same diameter the entire length.
The A2 barrel is larger under under the sight post all the way to the end of the barrel, minus threaded area. The pictures in your catalog confirm this.
I just wanted to know if they were the exact same diameter. Kurt at KKF assures me they are.
You are correct as to the use of the heavy slipover flash hider. The diameter under the front sight post to the end of the barrel is the same on an A2 barrel M4 barrel and a heavy barrel.